1. Field of the Invention
The present invention relates to a serial printer and a print control method which reduce misalignment between forward printing and backward printing due to a change in ambient temperature.
2. Description of the Related Art
Conventionally, a serial printer conducts, as a high speed printing means, reciprocating printing (bidirectional printing) in which printing is performed both at the time of left movement and at the time of right movement, in order to improve throughput.
In the bidirectional printing, misalignment (print misalignment of backward printing relative to forward printing) is caused by backlash of a driving section such as a gear, a drive shaft or a timing belt in a carriage mechanism, shift of motor load or ribbon load, etc. It is known that the misalignment varies according to the ambient temperature in the printer (actually, the temperature of the printer itself). As the temperature decreases, the backlash, motor load or ribbon load increases, that is, the amount of misalignment tends to increase. Therefore, there has been proposed a technique in which an ambient temperature is measured at the time of printing so that a time delay is applied to printing timing of opposite direction printing to one direction printing in accordance with misalignment pre-measured at the measured temperature to thereby prevent the misalignment (e.g., see JP-A-58-8666, JP-A-62-286778 and JP-A-4-82764).
In a printer capable of performing bidirectional printing, the amount of misalignment usually varies according to deterioration with age or external factors even in the case where the temperature does not change remarkably. In JP-A-58-8666, JP-A-62-286778 and JP-A-4-82764, there is however a problem that a satisfactory misalignment correction value cannot be obtained when the amount of misalignment varies according to deterioration with age or external factors because the misalignment correction value is a fixed value.
On the other hand, there is a printer provided with a correction value setting function in which a misalignment correction value can be set by an operator. In such a printer, there is however a problem as follows. For example, when adjustment is performed outdoors at a low temperature, correlation between the estimated amount of misalignment and the actual amount of misalignment is broken if the actual service environment is at a high temperature. Accordingly, the misalignment cannot be adequately corrected even when the setting function is merely provided.